package com.hmdp.utils;


import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Component;

import javax.annotation.Resource;
import java.time.LocalDateTime;
import java.time.ZoneOffset;
import java.time.format.DateTimeFormatter;

@Component
public class RedisIdWorker {
    private static final long BEGIN_TIMESTAMP = 1640995200L;//开始时间戳
    private static final long COUNT_BITS = 32;//序列号位数

    @Resource
    StringRedisTemplate stringRedisTemplate;

    public long nextId(String keyPrefix) {
        //1.时间戳
        LocalDateTime now = LocalDateTime.now();
        long nowSecond = now.toEpochSecond(ZoneOffset.UTC);
        long timestamp = nowSecond - BEGIN_TIMESTAMP;
        //2.序列号
        String date = now.format(DateTimeFormatter.ofPattern("yyyy:MM:dd"));
        //increment会自动创建不存在的key，所以不存在空指针异常
        long count = stringRedisTemplate.opsForValue().increment("icr:" + keyPrefix + ":" + date);//加一个date就可以保证每天都可以有2^32个序列
        //拼接生成
        return timestamp << COUNT_BITS | count;//这里使用位运算和或运算来拼接id，非常巧妙，可以看看视频理解
    }

    public static void main(String[] args) {
        LocalDateTime time = LocalDateTime.of(2022, 1, 1, 0, 0, 0);
        long second = time.toEpochSecond(ZoneOffset.UTC);
        System.out.println("second= " + second);
    }


}
